The Permian basin saw a surge in mergers and acquisitions this year, with the total value already exceeding a record $100 billion, led by the mega deals announced by ExxonMobil and Chevron, energy consultancy Wood Mackenzie said on Tuesday.

The Permian, the top oil-producing basin in the United States, saw a return of M&A activity this year as large operators look to add more acreage and expand their reserves and production.

The latter part of 2023 saw major deals announced, including $50-billion-plus deals for each of Exxon and Chevron.

In October, Exxon announced a deal to buy Pioneer Natural Resources in an all-stock transaction valued at $59.5 billion. The implied total enterprise value of the transaction, including net debt, is approximately $64.5 billion.

Exxon said back then that the proposed transaction “transforms ExxonMobil’s upstream portfolio, more than doubling the company’s Permian footprint and creating an industry-leading, high-quality, high-return undeveloped U.S. unconventional inventory position.”

Weeks later, Chevron said it would buy Hess Corporation in an all-stock transaction valued at $53 billion with a total enterprise value, including debt, at $60 billion.

The frenetic deal-making this year also included Permian Resources buying Earthstone Energy in an all-stock deal valued at $4.5 billion, which is expected to create a $14-billion premier producer in the Delaware basin in the Permian.

The latest announced deal was Monday’s statement from Occidental Petroleum, which said it would buy Permian oil and gas producer CrownRock for cash and stock in a deal valued at around $12 billion, including debt.

The acquisition will boost Occidental’s premier Permian portfolio with the addition of around 170,000 barrels of oil equivalent per day (boed) of high-margin, lower-decline unconventional production in 2024, as well as approximately 1,700 undeveloped locations, Oxy said.

“This transaction cements an absolute banner year in Permian acquisitions and divestments spend,” Robert Clarke, vice president of upstream research at Wood Mackenzie, said in a statement carried by Reuters.

“Coupled with other mega 2023 deals like ExxonMobil and Pioneer, it solidifies Permian scale and multi-decade longevity as a ‘must have’ trait for US Majors and Super-Independents.”